Recently, image processing machines using an electrophotographic image forming apparatus by an electrophotographic image forming process have made remarkable development. An electrophotographic image forming apparatus is one which forms images on a recording medium (for example, recording paper, OHP sheet or the like) by a process of electrophotographic image formation. Examples of such an electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, laser printer, LED printer or the like), a facsimile apparatus, a word processor and their combinations (multi-function printer or the like).
In the past, there were used inorganic photoreceptors employing inorganic compounds such as a selenium compound as a photoreceptor used in a laser printer or a digital copying machine of an electrophotographic image forming apparatus. Recently, there have been used organic photoreceptors employing organic compounds which make it easy to develop materials responsive to light of various wavelengths and also have little impact on the environments.
In an electrophotographic image forming apparatus by a process of electrophotographic image formation (hereinafter, also denoted simply as an image forming apparatus), the outer circumferential surface of a photosensitive layer of a drum-form electrophotographic photoreceptor (hereinafter, also denoted as simply as photoreceptor) which has been uniformly electrostatic-charged, is selectively exposes based on image data to form an electrostatic latent image thereon. The thus formed electrostatic latent image is developed with a toner (developer) by a developing means to form a toner image. Then the toner image is transferred to a recording medium to form then image. Further, after having transferred the toner image, a developer or the like remaining on the outer circumferential surface of the photosensitive layer of the photoreceptor is removed by a cleaning means. The photoreceptor, the outer circumferential surface of which has been cleaned by a cleaning means, is subjected to the next image formation process. Thus, in the outer circumferential surface of a photosensitive layer of a photoreceptor used for image formation in an image forming apparatus, image formation is performed through a series of repeated steps of electrostatic-charging, exposure, development, transfer and cleaning.
In an image forming apparatus by a process of electrophotographic image formation, there has been studied reduction of friction coefficient of the photosensitive layer surface of a photoreceptor with the aim of reducing the remaining toner amount after transfer as well as prevention of adhesion of an unwanted toner. It is known that this renders it difficult to cause cleaning trouble when cleaning a toner remaining on the photosensitive layer without being transferred by a blade or a brush. There are also known environmental effects such that a residual toner amount after transfer is reduced, leading to reduction of the waste toner amount, reduced torque to drive a photoreceptor and reduced electric power consumption of the image forming apparatus.
There is generally known a method of cleaning a residual toner on a photosensitive layer after transfer by a blade formed of urethane rubber or the like, which is brought into contact in the counter direction.
Meanwhile, development of a polymerization toner produced through emulsion polymerization, suspension polymerization or the like has been advanced along with recent demand for higher image quality in the market. However, such a polymerization toner easily causes cleaning trouble, as compared to irregular-shaped toner particles, resulting in image deterioration due to toner filming or fusion and leading to demand for further precise cleaning. The outer surface of a photosensitive layer and a blade, both of which are made of a resin, are insufficient in lubrication, and a blade easily reverses on the smooth surface of the photosensitive layer, often causing cleaning trouble.
To resolve problems of cleaning trouble, there is known addition of a lubricant to the photosensitive layer surface to reduce friction coefficient. Examples of a lubricant include a fluorine-containing resin (hereinafter, also denoted as a fluororesin) such as polytetrafluoroethylene, a spherical acryl resin, a powdery polyethylene, a powdery metal oxide such as silicon oxide or aluminum oxide, and a lubricant liquid such as silicone oil. Specifically, a fluororesin containing a relatively large amount of fluorine atoms exhibits a markedly reduced surface energy and results in enhanced lubricating effects. However, reduction of friction coefficient by these methods often produces problems such that contact with a blade over a long period of time results in a gradual increase of friction coefficient, leading to increased friction with the blade and causing troubles such as abnormal noise of the blade, torsion or the like.
Alternatively, since abrading the photosensitive layer surface of the photoreceptor with an abrasive to roughen the surface results in reduced contact area with the blade and makes it easy to remove foreign materials adhered thereto, Japanese Patent Application JP 2007-192906A describes a method in which surface-roughening of the photoreceptor surface is conducted by a sheet-form abrasive member, called abrasive sheet having a structure of providing abrasive grains dispersed in a resin on a substrate. However, abrasion by use of such an abrasion member of abrasive grain dispersion produced a problem such that the abrasive member surface was clogged with abrasive residue produced in abrasion, rendering it difficult to perform stable abrasion.
To resolve such a problem, for example, there is known an abrasive tape in which agglomerates (aggregative material) containing abrasive grains are regularly arranged to prevent abrasive residues from clogging the abrasive member surface, as described in, for example, JP 2008-216307A.
The use of an abrasive tape described in JP 2008-216307A has proved to be effective to prevent clogging of abrasive residue but led to problems described below:
1. Regular arrangement of abrasive grain-containing agglomerates and point-contact of the top of the agglomerates with the photoreceptor surface easily produces streak-like flaws on abrasion,
2. Production of streak-like flaws on the photoreceptor surface make it difficult to adhere a toner onto the flawed portion, easily causing white flaw troubles, and
3. Highly precise control is required when pressing the abrasive tape against the photoreceptor surface.
In view of the foregoing, there has been desired development of a surface abrasion method of the a photosensitive layer of a photoreceptor which prevents abrasive residue from clogging an abrasive tape, does not require highly precise control when pressing the abrasive tape onto the photoreceptor surface and produces no streak-like flaw on the photoreceptor surface when abrading the photosensitive layer surface of a photoreceptor by an abrasive tape.